Polypropylene films

ABSTRACT

The present invention provides isotactic polypropylene compositions suitable for cast film applications, cast polypropylene films made therefrom, and processes for forming such films. The novel polypropylene films are formed from film resins having a melt flow ratio of from 6–15 dg/min, with a narrow molecular weight distribution, narrow composition distribution, low level of solvent extractables, and increased film clarity (i.e., decreased haze %) compared to prior art Ziegler-Natta polypropylene film resins. The polypropylene films can be cast from an extruded polypropylene polymer, the extruded isotactic polypropylene polymer being formed by polymerization with a fluorided silica supported catalyst.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Nos.60/227,101, filed Aug. 22, 2000, and 60/263,368, filed Jan. 23, 2001,herein incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to isotactic polypropylenepolymers for non-oriented (cast) films, and also in general to α-olefinpolymer films formed from supported metallocene catalysts.

BACKGROUND

A variety of polymeric materials have been used successfully in thinnon-oriented (cast) films. A typical film casting process includes thesteps of polymer extrusion, melt feeding through a slot die, meltdraw-down in the air gap, chill-roll casting, edge-trim slitting,surface treating if necessary, and winding. With the development offaster, more robust winding technologies, cast film line speeds havebeen increasing in recent years. This increase in line speeds has led toimprovements in productivity and manufacturing economics. In this highlycompetitive segment of the film market, a versatile resin capable ofbeing processed at high line speeds, drawn-down to a thin and uniformweb, efficiently quenched to a clear film, and with a good profile offilm properties is very desirable.

Polypropylene can be used to make cast film materials having utility ina variety of important commercial applications. The processability andmany important end properties of the polymer are closely related topolymer characteristics such as molecular weight, molecular weightdistribution (“MWD”), composition distribution (“CD”) andstereoregularity, and these properties in turn are influenced by thecatalyst system used to make the polypropylene. Since the introductionof polypropylene in the 1950s, it has been a major interest and trend tomanipulate these polymer characteristics to address product needs.Conventional Ziegler-Natta catalysts have long been used to produceisotactic polypropylene. The development of efficient metallocene-basedcatalyst systems has led to the ability to precisely control polymercharacteristics, such as molecular weight, molecular weight distributionand composition distribution over a wide range unattainable by theconventional Ziegler-Natta catalysts.

There remains a need for an improved metallocene catalyzed polypropylenesuitable for high output film processing, and supported metallocenecatalyst systems capable of efficiently producing polypropylene for castfilm applications.

SUMMARY OF THE INVENTION

The present invention provides novel isotactic polypropylenecompositions suitable for cast film applications, and cast polypropylenefilms made therefrom. In one embodiment, the present invention providesa polypropylene film having a melt flow rate (“MFR”) of from 6–15 dg/minin one embodiment, and from 9–12 dg/min in another embodiment, with anarrow molecular weight distribution, narrow composition distribution,low level of solvent extractables, and increased film clarity (i.e.,decreased haze %) compared to prior art Ziegler-Natta polypropylenefilms. In this embodiment, the polypropylene film is cast from anextruded polypropylene polymer, the extruded polypropylene polymer beingformed by polymerization with a novel fluorided silica supportedcatalyst.

In another embodiment, the present invention provides a process forproducing a polypropylene film having an MFR of from 6–15 dg/min in oneembodiment, and from 9–12 dg/min in another embodiment, with a narrowmolecular weight distribution, narrow composition distribution, lowlevel of solvent extractables, and increased film clarity compared toprior art Ziegler-Natta polypropylene films. The xylene extractables (orsolubles) level of the polymer is less than 2 wt % in one embodiment,less than 1.5 wt % in another embodiment, and less than 1% in anotherembodiment, the wt % relative to the total polymer. The recoverablecompliance for the polymers of the invention is from 0.5 to 1.8(Pa⁻¹×1⁻⁴) in one embodiment, and from 0.6 to 1.5 (Pa⁻¹×1⁻⁴) in anotherembodiment. Further, the MWD (Mw/Mn) is less than 3 in one embodiment,less than 2.8 in another embodiment, and less than 2.5 in yet anotherembodiment.

The process includes the steps of forming a polypropylene polymer bypolymerization of propylene monomers in the presence of a fluoridedsilica supported catalyst, and casting the resultant polypropylene toform a cast polypropylene film having the above-described properties.

In another embodiment, the present invention provides a polypropylenefilm produced by a process including the steps of forming apolypropylene polymer by polymerization of propylene monomers and atleast one α-olefin or ethylene comonomer in the presence of a fluoridedsilica supported catalyst, and casting the resultant polypropylene toform a cast polypropylene film.

In another embodiment, the present invention provides articles ofmanufacture formed of or including a cast polypropylene film asdescribed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a simplified schematic diagram of a typical castingapparatus;

FIG. 2 shows the molecular weight distribution of a metallocenepolypropylene polymer of the present invention compared to aZiegler-Natta polymer having the same MFR;

FIG. 3 shows the composition distribution of an invention randomcopolymer versus a Ziegler-Natta random copolymer;

FIG. 4 compares the loss modulus (viscous strain) versus storage modulus(elastic strain) for an invention film and a typical Ziegler-Nattacatalyzed film;

FIG. 5 compares the extrudability of an invention polymer andZiegler-Natta polymer using a monolayer casting process, using a 89 mmextruder, 107 cm die at 0.635 mm die gap, 125 rpm screw speed and 21° C.chill roll;

FIG. 6 compares the MFR shift of invention and Ziegler-Natta polymersafter multiple extrusions at 260° C.; and

FIG. 7 compares the color shift of invention and Ziegler-Natta polymersafter multiple extrusions at 260° C.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides polypropylene polymers suitable for castfilm applications, having improved processability and filmcharacteristics, such as film clarity. These advantageous features areachieved by using a novel metallocene catalyst to form the polypropylenefilm resins, i.e., the resins used to form the films of the presentinvention. Resins used to form the present films, formed as describedbelow, have an MFR of 6–15 dg/min in one embodiment, and from 9–12dg/min in another embodiment.

The polymers of α-olefins of the present invention can be formed with asupported metallocene catalyst system. Although the following materialsdiscuss preferred supported metallocene catalyst systems in greatdetail, it should be appreciated that the catalyst system can be anyconventional supported metallocene catalyst system, and the invention isnot limited to the preferred systems described herein.

Preferably, the metallocene catalyst system is the product of contactingat least three components: (1) one or more metallocenes; (2) one or moreactivators; and (3) one or more fluorided support compositions.

Definitions

As used herein, the phrase “fluorided support” or “fluorided supportcomposition” means a support, desirably particulate and porous, whichhas been contacted with at least one inorganic fluorine containingcompound. For example, the fluorided support composition can be asilicon dioxide support wherein a portion of the silica hydroxyl groupshas been replaced with fluorine or fluorine containing compounds.

As used herein, the numbering scheme for the Periodic Table Groups areused as in HAWLEY'S CONDENSED CHEMICAL DICTIONARY 852 (13th ed. 1997).

As used herein, the term “polypropylene” refers to homopolymers orcopolymers made propylene derived units, and C₃ to C₁₂ α-olefin derivedunits when a copolymer.

As used herein, the terms “catalyst system” and “metallocene catalystsystem” include at least one or more metallocenes, and at least onesecondary component such as activators and cocatalysts, of whichalumoxanes and boranes are broad classes of such compounds, and at leastone support such as a silica support which may be fluorided which mayalso be present.

Metallocene Component

The terms “catalyst system” and “metallocene catalyst system” include atleast a primary catalyst component such as a metallocene, and secondarycomponents such as activators and cocatalysts, of which alumoxanes andboranes are broad classes of such compounds which may also be present,and a support such as a silica support that may be fluorided which mayalso be present.

The catalyst system of the present invention has as a component at leastone metallocene. As used herein “metallocene” refers generally tocompounds represented by the formula Cp_(m)MR_(n)X_(q) wherein Cp is acyclopentadienyl ring which may be substituted, or derivative thereofwhich may be substituted, M is a Group 4, 5, or 6 transition metal, forexample titanium, zirconium, halfnium, vanadium, niobium, tantalum,chromium, molybdenum and tungsten, R is a hydrocarbyl group orhydrocarboxy group having from one to 20 carbon atoms, X is a halogen orhydrogen, and m=1–3, n=0–3, q=0–3, and the sum of m+n+q is equal to theoxidation state of the transition metal.

Methods for making and using metallocenes are disclosed in, for exampleU.S. Pat. Nos. 4,530,914; 4,542,199; 4,769,910; 4,808,561; 4,871,705;4,933,403; 4,937,299; 5,017,714; 5,026,798; 5,057,475; 5,120,867;5,278,119; 5,304,614; 5,324,800; 5,350,723, 6,143,686; and 5,391,790.

One embodiment of the metallocenes used in the catalyst system of theinvention are represented by the structure (1):

wherein M is a metal of Group 4, 5, or 6 of the Periodic Table,zirconium (Zr), halfnium (Hf) or titanium (Ti) in one embodiment.

In structure (1), R¹ and R² are identical or different, and are one of ahydrogen atom, a C₁–C₁₀ alkyl group, a C₁–C₃ alkyl group in anotherembodiment, a C₁–C₁₀ alkoxy group, a C₁–C₃ alkoxy group in anotherembodiment, a C₆–C₁₀ aryl group, a C₆–C₈ aryl group in anotherembodiment, a C₆–C₁₀ aryloxy group, a C₆–C₈ aryloxy group in anotherembodiment, a C₂–C₁₀ alkenyl group, a C₂–C₄ alkenyl group in anotherembodiment, a C₇–C₄₀ arylalkyl group, a C₇–C₁₀ arylalkyl group inanother embodiment, a C₇–C₄₀ alkylaryl group, a C₇–C₁₂ alkylaryl groupin another embodiment, a C₈–C₄₀ arylalkenyl group, a C₈–C₁₂ arylalkenylgroup in another embodiment, or a halogen atom, preferably chlorine. Inanother embodiment, R₁ and R₂ can be an alkyl diene or other dienecompound that is able to provide two points of unsaturation forassociation with the metal center M of (1).

In structure (1), R⁵ and R⁶, being in the so called “2” position on theindenyl ring, are identical or different and are one of a halogen atom,a fluorine, chlorine or bromine atom in one embodiment, a C₁–C₁₀ alkylgroup, a C₁–C₄ alkyl group in another embodiment, which may behalogenated, a C₆–C₁₀ aryl group, which may be halogenated, a C₆–C₈ arylgroup in another embodiment, a C₂–C₁₀alkenyl group, a C₂–C₄ alkenylgroup in another embodiment, a C₇–C₄₀ arylalkyl group, a C₇–C₁₀arylalkyl group in another embodiment, a C₇–C₄₀ alkylaryl group, aC₇–C₁₂ alkylaryl group in another embodiment, a C₈–C₄₀ arylalkenylgroup, a C₈–C₁₂ arylalkenyl group in another embodiment, a —NR₂ ¹⁵,—SR¹⁵, —OR¹⁵, —OSiR₃ ¹⁵ or —PR₂ ¹⁵ radical, wherein R¹⁵ is one of ahalogen atom, a chlorine atom in another embodiment, a C₁–C₁₀ alkylgroup, a C₁–C₃ alkyl group in another embodiment, or a C₆–C₁₀ arylgroup, a C₆–C₉ aryl group in another embodiment.

Also, in structure (1), R⁷ is

—B(R¹¹)—, —Al(R¹¹)—, —Ge—, —Sn—, —O—, —S—, —SO—, —SO₂—, —N(R¹¹)—, —CO—,—P(R¹¹)—, or —P(O)(R¹¹)—, wherein R¹¹, R¹² and R¹³ are identical ordifferent and are a hydrogen atom, a halogen atom, a C₁–C₂₀ alkyl group,a C₁–C₁₀ alkyl group in another embodiment, a C₁–C₂₀ fluoroalkyl group,a C₁–C₁₀ fluoroalkyl group in another embodiment, a C₆–C₃₀ aryl group, aC₆–C₂₀ aryl group in another embodiment, a C₆–C₃₀ fluoroaryl group, aC₆–C₂₀ fluoroaryl group in another embodiment, a C₁–C₂₀ alkoxy group, aC₁–C₁₀ alkoxy group in another embodiment, a C₂–C₂₀ alkenyl group, aC₂–C₁₀ alkenyl group in another embodiment, a C₇–C₄₀ arylalkyl group, aC₇–C₂₀ arylalkyl group in another embodiment, a C₈–C₄₀ arylalkenylgroup, a C₈–C₂₂ arylalkenyl group in another embodiment, a C₇–C₄₀alkylaryl group, a C₇–C₂₀ alkylaryl group in another embodiment, or R¹¹and R¹², or R¹¹ and R¹³, together with the atoms binding them, can formring systems.

In structure (1), M² is silicon (Si), germanium (Ge) or tin (Sn),silicon (Si) or germanium (Ge) in one embodiment, and most desirablysilicon (Si). Also, R⁸ and R⁹ are identical or different and have themeanings stated for R¹¹. Further, m and n are identical or different andare zero, 1 or 2, zero or 1 in one embodiment, and m plus n being zero,1 or 2, desirably zero or 1.

Finally, in structure (1), the radicals R¹⁰ are identical or differentand have the meanings stated for R¹¹, R¹² and R¹³. In one embodiment,R¹⁰ is a phenyl group. The R¹⁰ group or groups can be substituted on anyposition or positions on the indenyl ring system that is not alreadysubstituted as described above. Two adjacent R¹⁰ radicals can be joinedtogether to form a ring system, preferably a ring system containing from4–6 carbon atoms.

Alkyl refers to straight or branched chain saturated, non-aromatichydrocarbyl substituents. Alkenyl refers to strait or branched chainunsaturated substituents. Halogen (halogenated) refers to fluorine,chlorine, bromine or iodine atoms, preferably fluorine or chlorine. Arylrefers to cyclic aromatic moieties such as phenyl or naphthyl. Alkylarylrefers to an alkyl-substituted aryl moiety, and arylalky refers to anaryl-substituted alkyl moiety.

In another embodiment, the metallocene component is a compound of thestructures (2) or (3):

wherein M¹ is zirconium (Zr) or halfnium (Hf), R¹ and R² are methyl orchlorine, and R⁵, R⁶, R⁸, R⁹, R¹⁰, R¹¹ and R¹² have the above-mentionedmeanings.

The molecules represented by structures (1) through (3) can exist asboth chiral and achiral structures. These chiral metallocenes may beused as a racemic (rac) mixture for the preparation of highly isotacticpolyolefinic polymers such as isotactic polypropylene homopolymer orcopolymer. It is also possible to use the pure R or S form. An opticallyactive polymer can be prepared with these pure stereoisomeric forms.Preferably, the meso form of the metallocene is removed to ensurestereoregular polymerization takes place when the metallocene is used asa polymerization catalyst. For special products it is also possible touse rac/meso mixtures. Separation of the stereoisomers can beaccomplished by known literature techniques.

Illustrative but non-limiting examples of the at least one metallocenecomponent of the catalyst system includes the following:

-   Dimethylsilandiylbis(2-methyl-4-phenyl-1-indenyl)zirconium    dichloride-   Dimethylsilandiylbis(2-methyl-4,5-benzoindenyl)zirconium dichloride;-   Dimethylsilandiylbis(2-methyl-4,6-diisopropylindenyl)zirconium    dichloride;-   Dimethylsilandiylbis(2-ethyl-4-phenyl-1-indenyl)zirconium    dichloride;-   Dimethylsilandiylbis(2-methyl-4-(α-naphthyl)-1-indenyl)zirconium    dichloride-   Dimethylsilandiylbis(2-ethyl-4-(α-naphthyl)-1-indenyl)zirconium    dichloride-   Dimethylsilandiylbis(2-methyl-4-(β-naphthyl)-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2-ethyl-4-(β-naphthyl)-1-indenyl)zirconium    dichloride-   Phenyl(methyl)silandiylbis(2-methyl-4-phenyl-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2-methyl-4-(1-naphthyl)-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2-methyl-4-(2-napbthyl)-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2-methyl-indenyl)zirconium dichloride,-   Dimethylsilandiylbis(2-methyl-4,5-diisopropyl-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2,4,6-trimethyl-1-indenyl)zirconium dichloride,-   Phenyl(methyl)silandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)zirconium    dichloride,-   1,2-Ethandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)zirconium    dichloride,-   1,2-Butandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2-methyl-4-ethyl-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2-methyl-4-isopropyl-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2-methyl-4-t-butyl 1-indenyl)zirconium    dichloride,-   Phenyl(methyl)silandiylbis(2-methyl-4-isopropyl-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2-ethyl-4-methyl-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2,4-dimethyl-1-indenyl)zirconium dichloride,-   Dimethylsilandiylbis(2-methyl-4-ethyl-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2-methyl-4-(5-acenaphthyl)-1-indenyl)zirconium    dichloride,-   Phenyl(methyl)silandiylbis(2-methyl-4,5-benzo-1-indenyl)zirconium    dichloride,-   Phenyl(methyl)silandiylbis(2-methyl-4,5-(methylbenzo)-1-indenyl)zirconium    dichloride,-   Phenyl(methyl)silandiylbis(2-methyl-4,5-(tetramethylbenzo)-1-indenyl)zirconium    dichloride,-   Phenyl(methyl)silandiylbis(2-methyl-4-(5-acenaphthyl)-1-indenyl)zirconium    dichloride,-   1,2-Ethandiylbis(2-methyl-4,5-benzo-1-indenyl)zirconium dichloride,-   1,2-Butandiylbis(2-methyl-4,5-benzo-1-indenyl)zirconium dichloride,-   Dimethylsilandiylbis(2-methyl-4,5-benzo-1-indenyl)zirconium    dichloride,-   1,2-Ethandiylbis(2,4,7-trimethyl-1-indenyl)zirconium dichloride,-   Dimethylsilandiylbis(2-methyl-1-indenyl)zirconium dichloride,-   1,2-Ethandiylbis(2-methyl-1-indenyl)zirconium dichloride,-   Phenyl(methyl)silandiylbis(2-methyl-1-indenyl)zirconium dichloride,-   Diphenylsilandiylbis(2-methyl-1-indenyl)zirconium dichloride,-   1,2-Butandiylbis(2-methyl-1-indenyl)zirconium dichloride,-   Dimethylsilandiylbis(2-ethyl-1-indenyl)zirconium dichloride,-   Dimethylsilandiylbis(2-methyl-5-isobutyl-1-indenyl)zirconium    dichloride,-   Phenyl(methyl)silandiylbis(2-methyl-5-isobutyl-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2-methyl-5-t-butyl-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2,5,6-trimethyl-1-indenyl)zirconium dichloride,-   Dimethylsilandiylbis(2-methyl-4-phenyl-1-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-methyl-4,5-benzoindenyl)zirconium dimethyl;-   Dimethylsilandiylbis(2-methyl-4,6-diisopropylindenyl)zirconium    dimethyl;-   Dimethylsilandiylbis(2-ethyl-4-phenyl-1-indenyl)zirconium dimethyl;-   Dimethylsilandiylbis(2-methyl-4-α-naphthyl)-1-indenyl)zirconium    dimethyl-   Dimethylsilandiylbis(2-ethyl-4-(α-naphthyl)-1-indenyl)zirconium    dimethyl-   Dimethylsilandiylbis(2-methyl-4-(β-naphthyl)-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-ethyl-4-(β-naphthyl)-1-indenyl)zirconium    dimethyl-   Phenyl(methyl)silandiylbis(2-methyl-4-phenyl-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-methyl-4-(1-naphthyl)-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-methyl-4-(2-naphthyl)-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-methyl-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-methyl-4,5-diisopropyl-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2,4,6-trimethyl-1-indenyl)zirconium dimethyl,-   Phenyl(methyl)silandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)zirconium    dimethyl,-   1,2-Ethandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)zirconium    dimethyl,-   1,2-Butandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-methyl-4-ethyl-1-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-methyl-4-isopropyl-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-methyl-4-t-butyl-1-indenyl)zirconium    dimethyl,-   Phenyl(methyl)silandiylbis(2-methyl-4-isopropyl-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-ethyl-4-methyl-1-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2,4-dimethyl-1-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-methyl-4-ethyl-1-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-methyl-4-(5-acenaphthyl)-1-indenyl)zirconium    dimethyl,-   Phenyl(methyl)silandiylbis(2-methyl-4,5-benzo-1-indenyl)zirconium    dimethyl,-   Phenyl(methyl)silandiylbis(2-methyl-4,5-(methylbenzo)-1-indenyl)zirconium    dimethyl,-   Phenyl(methyl)silandiylbis(2-methyl-4,5-(tetramethylbenzo)-1-indenyl)zirconium    dimethyl,-   Phenyl(methyl)silandiylbis(2-methyl-4-(5-acenaphthyl)-1-indenyl)zirconium    dimethyl,-   1,2-Ethandiylbis(2-methyl-4,5-benzo-1-indenyl)zirconium dimethyl,-   1,2-Butandiylbis(2-methyl-4,5-benzo-1-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-methyl-4,5-benzo-1-indenyl)zirconium    dimethyl,-   1,2-Ethandiylbis(2,4,7-trimethyl-1-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-methyl-1-indenyl)zirconium dimethyl,-   1,2-Ethandiylbis(2-methyl-1-indenyl)zirconium dimethyl,-   Phenyl(methyl)silandiylbis(2-methyl-1-indenyl)zirconium dimethyl,-   Diphenylsilandiylbis(2-methyl-1-indenyl)zirconium dimethyl,-   1,2-Butandiylbis(2-methyl-1-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-ethyl-1-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-methyl-5-isobutyl-1-indenyl)zirconium    dimethyl,-   Phenyl(methyl)silandiylbis(2-methyl-5-isobutyl-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-methyl-5-t-butyl-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2,5,6-trimethyl-1-indenyl)zirconium dimethyl,    and the like.

These metallocene catalyst components are described in detail in U.S.Pat. Nos. 6,143,686, 5,145,819; 5,243,001; 5,239,022; 5,329,033;5,296,434; and 5,276,208; and 5,374,752; and EP 549 900 and 576 970.Typically, these metallocenes can be described asbis(substituted-indenyl) metallocenes. In one embodiment of theinvention, a bis(substituted-indenyl) metallocene is a component of thecatalyst system, the bis(substituted-indenyl) metallocene including boththe dichloride and dimethyl-Group 4 metal.

In yet another embodiment of the invention, the metallocene component isa bridged 2,4 di-substituted indenyl metallocene, wherein at least the 2and 4 positions on the indenyl ring are substituted as described instructure (1). Examples of such metallocenes are rac-:

-   Dimethylsilandiylbis(2-methyl-4-phenyl-1-indenyl)zirconium    dichloride,-   Dimethylsilandiylbis(2,4-dimethylindenyl)zirconium dichloride,-   Dimethylsilandiylbis(2,5,6-trimethylindenyl)zirconium dichloride,-   Dimethylsilandiylbis(4,5,6,7-tetrahydroindenyl)zirconium dichloride,-   Dimethylsilandiylbis(2-methyl-4,5-benzoindenyl)zirconium dichloride,-   Dimethylsilandiylbis(2-methyl-4-phenyl-1-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-methyl-4,5-benzoindenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-methyl-4,6-diisopropylindenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-ethyl-4-phenyl-1-indenyl)zirconium dimethyl,-   Dimethylsilandiylbis(2-methyl-4-(α-naphthyl)-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-methyl-4-(β-naphthyl)-1-indenyl)zirconium    dimethyl,-   Phenyl(methyl)silandiylbis(2-methyl-4-phenyl-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-methyl-4-(1-naphthyl)-1-indenyl)zirconium    dimethyl,-   Dimethylsilandiylbis(2-methyl-4-(2-naphthyl)-1-indenyl)zirconium    dimethyl, and-   Dimethylsilandiylbis(2-methyl-indenyl)zirconium dimethyl.

In yet another embodiment of the invention, the metallocene component isa bridged 4-phenyl-1-indenyl substituted metallocene such asdimethylsilandiylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichlorideand phenyl(methyl)silandiylbis(2-methyl-4-phenyl-1-indenyl)zirconiumdimethyl, and the like, wherein the 2-position is substituted asdescribed in structure (1), and the 4-position is phenyl substituted.The bridged 4-phenyl-1-indenyl substituted metallocene may be describedin structure (4):

wherein R⁵, R⁶, R¹⁰, R¹¹ and R¹² are as defined above, M¹ is zirconium(Zr) or halfnium (Hf), and R¹ and R² are either a halogen, hydrogen, ormethyl, the phenyl group is in the so called “4” position on the indenylring. R⁵ and R⁶ are C₁ to C₅ alkyl groups in a desirable embodiment.Embodiments of the structure (3) aredimethylsilandiylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichloride,phenyl(methyl)silandiylbis(2-methyl-4-phenyl-1-indenyl)zirconiumdichloride dimethylsilandiylbis(2-methyl-4-phenyl-1-indenyl)zirconiumdimethyl, andphenyl(methyl)silandiylbis(2-methyl-4-phenyl-1-indenyl)zirconiumdimethyl. When R¹ and/or R² are halogens such as chloride, the catalystsystem desirably includes a Lewis Acid such as an alkyl aluminumcompound, an example of which include triethylaluminum (TEAL) andmethylaluminumoxane (MAO).

The metallocene component selected for use in the catalyst system ofthis invention is a metallocene which, when used alone, producesisotactic, crystalline propylene polymer and when used in combinationwith another metallocene, produces polymer having the attributes desiredfor the particular application of interest. Desirable metallocenes arethose selected from formulas 2 and/or 3 which when used alone to producepropylene homopolymer, are capable of producing an isotactic polymerhaving a weight average molecular weight of from 25,000 to 200,000 atcommercially attractive temperatures of from 50° C. to 120° C.

In another embodiment of the invention, a comonomer may be used withpropylene to form a copolymer suitable for the fiber and fabric. Themetallocenes used may show different molecular weight responses when inthe presence of comonomer. This will also affect the molecular weightdistribution of the product. For example, we have found that theincorporation of up to 5 wt % comonomer such as a C₂ to C₁₂ α-olefincomonomer in one embodiment, and up to 5 wt % ethylene comonomer inanother embodiment, during the polymerization process as describedherein results in a substantial broadening of the molecular weightdistribution at the high molecular weight end.

Additional broadening of molecular weight distribution may be practicedthrough reactor process techniques. For example, operating the differentstages of a multiple stage polymerization process with varying levels ofhydrogen, a molecular weight regulator, is known in the art to producebroadening of molecular weight distribution. Also, the resin may bespiked post blend with a Ziegler-Natta produced polymer, or otherpolymer having a very low or high MFR.

In another embodiment of the invention, a comonomer may be used withpropylene to form a copolymer suitable for the fiber and fabric. Themetallocenes used may show different molecular weight responses when inthe presence of comonomer. This will also affect the molecular weightdistribution of the product. For example, we have found that theincorporation of up to 10 wt % comonomer such as a C₂ to C₁₂ α-olefincomonomer in one embodiment, and up to 5 wt % ethylene comonomer inanother embodiment, during the polymerization process as describedherein results in a substantial broadening of the molecular weightdistribution at the high molecular weight end.

Activators

Embodiments of the activator component are herein described.Metallocenes are generally used in combination with some form ofactivator in order to create an active catalyst system. The term“activator” is defined herein to be any compound or component, orcombination of compounds or components, capable of enhancing the abilityof one or more metallocenes to polymerize olefins to polyolefins.

In one embodiment, ionizing activators are used to activate themetallocenes. These activators can be “non-ionic” or “ionic” (alsocalled non-coordinating anion activators or NCA activators). The ionicactivators are compounds such as tri(n-butyl)ammoniumtetrakis(pentaflurophenyl)boron, which ionize the neutral metallocenecompound. Such ionizing compounds may contain an active proton, or someother cation associated with but not coordinated or only looselyassociated with the remaining ion of the ionizing compound. Combinationsof activators may also be used, for example, alumoxane and ionizingactivators in combinations, see for example, WO 94/07928. The non-ionicactivator precursors that can serve as the NCA activators are strongLewis acids with non-hydrolyzable ligands, at least one of which iselectron-withdrawing, such as those Lewis acids known to abstract ananionic fragment from dimethyl zirconocene (biscyclopentadienylzirconium dimethyl) e.g., trisperfluorophenyl boron,trisperfluoronaphthylboron, or trisperfluorobiphenyl boron, and otherhighly fluorinated trisaryl boron compounds.

The term “non-coordinating anion” describes an anion which either doesnot coordinate to the cationic metallocene or which is only weaklycoordinated to said cation thereby remaining sufficiently labile to bedisplaced by a neutral Lewis base. “Compatible” noncoordinating anionsare those which are not degraded to neutrality when the initially formedcomplex decomposes. Further, the anion will not transfer an anionicsubstituents or fragment to the cation so as to cause it to form aneutral four coordinate metallocene compound and a neutral by-productfrom the anion. Noncoordinating anions useful in accordance with thisinvention are those which are compatible, stabilize the metallocenecation in the sense of balancing its ionic charge in a +1 state, yetretain sufficient lability to permit displacement by an ethylenically oracetylenically unsaturated monomer during polymerization.

In a desirable embodiment of the invention, the activator andmetallocene components are contacted with a support such as a silicon orfluorided silicon support (discussed further below). Thus, these NCAactivator precursors typically do not possess any reactive ligands whichcan be protonated by the hydroxyl groups of the metal oxide (the silanolgroup proton) of the support, when present. For example, any Group 13element based Lewis acids having only alkyl, halo, alkoxy, and/or amidoligands, which are readily hydrolyzed in aqueous media, are notsuitable. At least one ligand of the NCA activator must be sufficientlyelectron-withdrawing to achieve the needed acidity, for example,trisperfluorophenyl boron, under typical reaction conditions.

Typical metal/metalloid centers for the NCA activator will includeboron, aluminum, antimony, arsenic, phosphorous and gallium. In oneembodiment, the NCA activator is a neutral compound comprising a Group13 metalloid center with a complement of ligands together sufficientlyelectron-withdrawing such that the Lewis acidity is greater than orequal to that of AlCl₃. Examples include trisperfluorophenylboron,tris(3,5-di(trifluoromethyl)phenyl)boron,tris(di-t-butylmethylsilyl)perfluorophenylboron, and other highlyfluorinated trisarylboron compounds. Other suitable activators aredisclosed by Chen and Marks, 100 Chemical Reviews 1392–1434 (2000); Yanget al., 116 J. Am. Chem. Soc. 10015–10031 (1994); Yang et al., 113 J.Am. Chem. Soc. 3623–3625 (1991); Chien et al. 113 J. Am. Chem. Soc.8570–8571 (1991); Bochmann et al. 12 Organometallics 633–640 (1999);Herfert et al. 14 Makromol. Chem., Rapid Commun. 91–96 (1993); and in EP0 704 463 and EP 0 513 380.

The use of ionizing ionic compounds not containing an active proton butcapable of producing both the active metallocene cation and anoncoordinating anion is also known. See, EP-A-0 426 637 and EP-A-0 573403. An additional method of making the ionic catalysts uses ionizinganion pre-cursors which are initially neutral Lewis acids but form thecation and anion upon ionizing reaction with the metallocene compounds,for example the use of tris(pentafluorophenyl) boron. See EP-A-0 520732. Ionic catalysts for addition polymerization can also be prepared byoxidation of the metal centers of transition metal compounds by anionpre-cursors containing metallic oxidizing groups along with the aniongroups, see EP-A-0 495 375. Examples of suitable ionic NCA activators,include:

trialkyl-substituted ammonium salts such as:

triethylammonium tetraphenylborate;

tripropylammonium tetraphenylborate;

tri(n-butyl)ammonium tetraphenylborate;

trimethylammonium tetrakis(p-tolyl)borate;

trimethylammonium tetrakis(o-tolyl)borate;

tributylammonium tetrakis(pentafluorophenyl)borate;

tripropylammonium tetrakis(o,p-dimethylphenyl)borate;

tributylammonium tetrakis(m,m-dimethylphenyl)borate;

tributylammonium tetrakis(p-trifluoromethylphenyl)borate;

tributylammonium tetrakis(pentafluorophenyl)borate; and

tri(n-butyl)ammonium tetrakis(o-tolyl)borate;

N,N-dialkyl anilinium salts such as:

N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate;

N,N-dimethylaniliniumtetrakis(heptafluoronaphthyl)borate;

N,N-dimethylanilinium tetrakis(perfluoro-4-biphenyl)borate;

N,N-dimethylanilinium tetraphenylborate;

N,N-diethylanilinium tetraphenylborate; and

N,N-2,4,6-pentamethylanilinium tetraphenylborate;

dialkyl ammonium salts such as:

di-(isopropyl)ammonium tetrakis(pentafluorophenyl)borate; and

dicyclohexylammonium tetraphenylborate; and

triaryl phosphonium salts such as:

triphenylphosphonium tetraphenylborate;

tri(methylphenyl)phosphonium tetraphenylborate; and

tri(dimethylphenyl)phosphonium tetraphenylborate.

Further examples of suitable ionic NCA activators include:

tropillium tetrakis(pentafluorophenyl)borate;

triphenylmethylium tetrakis(pentafluorophenyl)borate;

benzene (diazonium) tetrakis(pentafluorophenyl)borate;

tropillium phenyltris(pentafluorophenyl)borate;

triphenylmethylium phenyl-(trispentafluorophenyl)borate;

benzene (diazonium) phenyl-tris(pentafluorophenyl)borate;

tropillium tetrakis(2,3,5,6-tetrafluorophenyl)borate;

triphenylmethylium tetrakis(2,3,5,6-tetrafluorophenyl)borate;

benzene (diazonium) tetrakis(3,4,5-trifluorophenyl)borate;

tropillium tetrakis(3,4,5-trifluorophenyl)borate;

benzene (diazonium) tetrakis(3,4,5-trifluorophenyl)borate;

tropillium tetrakis(3,4,5-trifluorophenyl)aluminate;

triphenylmethylium tetrakis(3,4,5-trifluorophenyl)aluminate;

benzene (diazonium) tetrakis(3,4,5-trifluorophenyl)aluminate;

tropillinum tetrakis(1,2,2-trifluoroethenyl)borate;

triphenylmethylium tetrakis(1,2,2-trifluoroethenyl)borate;

benzene (diazonium) tetrakis(1,2,2-trifluoroethenyl)borate;

tropillium tetrakis(2,3,4,5-tetrafluorophenyl)borate;

triphenylmethylium tetrakis(2,3,4,5-tetrafluorophenyl)borate; and

benzene (diazonium) tetrakis(2,3,4,5-tetrafluorophenyl)borate.

In the embodiment where the metallocene component metal ligands includehalogen moieties (for example, bis-cyclopentadienyl zirconiumdichloride, wherein the R¹ and R² groups in structures 1–3 are ahalogen) which are not capable of ionizing abstraction under standardconditions, they can be converted via known alkylation reactions withorganometallic compounds such as lithium or aluminum hydrides or alkyls,alkylalumoxanes, Grignard reagents, etc. See EP-A-0 500 944 and EP-A1-0570 982 for in situ processes describing the reaction of alkyl aluminumcompounds with dihalo-substituted metallocene compounds prior to or withthe addition of activating anionic compounds. For example,triethaluminum (TEAL) or MAO can be used to form the in situ reactivemetallocene component.

In one embodiment of the catalyst system of the invention, the activatoris associated with the fluorided support material to form a fluoridedsupport composition. In another embodiment, the fluorided supportmaterial is associated with a metallocene to form a fluorided supportcomposition. In yet another embodiment of the invention, the fluoridedsupport is first associated with an activator, followed by associationwith a metallocene. In one embodiment, the activator is anon-coordinating anion. In another embodiment, the activator is bound tothe fluorided support, wherein the metallocene then associates with thesupport composition.

Support Composition

The metallocene catalyst systems used in the process of this inventionare preferably supported using a porous particulate material, such asfor example, talc, inorganic oxides, inorganic chlorides and resinousmaterials such as polyolefins or other polymeric compounds. Inparticular, the catalyst system is typically the resultant compositionfrom contacting at least the metallocene component, the activatorcomponent, and the support component.

Desirable support materials are porous inorganic oxide materials, whichinclude those from the Periodic Table of Elements of Groups 2, 3, 4, 5,13 or 14 metal oxides. Silica, alumina, silica-alumina, and mixturesthereof are particularly preferred. Other inorganic oxides that may beemployed either alone or in combination with the silica, alumina orsilica-alumina are magnesia, titania, zirconia, and the like.

In one embodiment, the support material is porous silica which has asurface area in the range of from 10 to 700 m²/g, a total pore volume inthe range of from 0.1 to 4.0 cc/g and an average particle size in therange of from 10 to 500 μm. Desirably, the surface area is in the rangeof from 50 to 500 m²/g, the pore volume is in the range of from 0.5 to3.5 cc/g and the average particle size is in the range of from 20 to 200μm. In yet another embodiment, the surface area is in the range of from100 to 400 m²/g, the pore volume is in the range of from 0.8 to 3.0 cc/gand the average particle size is in the range of from 30 to 100 μm. Theaverage pore size of typical porous support materials is in the range offrom 10 to 1000 Å. Desirably, a support material is used that has anaverage pore diameter of from 50 to 500 Å, and from 75 to 350 Å inanother embodiment. It may be desirable to dehydrate the silica at atemperature of from 100° C. to 800° C. anywhere from 3 to 24 hours.

In another embodiment of the support, the porous silica is fluorided bytreatment with a fluorine compound prior to reacting the support withthe metallocene or activator components. The fluorine compounds suitablefor providing fluorine for the support are desirably inorganic fluorinecontaining compounds. Such inorganic fluorine containing compounds maybe any compound containing a fluorine atom as long as it does notcontain a carbon atom. Particularly desirable are inorganic fluorinecontaining compounds selected from NH₄BF₄, (NH₄)₂SiF₆, NH₄PF₆, NH₄F,(NH₄)₂TaF₇, NH₄NbF₄, (NH₄)₂GeF₆, (NH₄)₂SmF₆, (NH₄)₂TiF₆, (NH₄)₂ZrF₆,MoF₆, ReF₆, GaF₃, SO₂ClF, F₂, SiF₄, SF₆, ClF₃, ClF₅, BrF₅, IF₇, NF₃, HF,BF₃, NHF₂ and NH₄HF₂. Of these, NH₄BF₄, (NH₄)₂SiF₆ are desirableembodiments.

Ammonium hexafluorosilicate and ammonium tetrafluoroborate fluorinecompounds are typically solid particulates as are the silicon dioxidesupports. A desirable method of treating the support with the fluorinecompound is to dry mix the two components by simply blending at aconcentration of from 0.01 to 10.0 millimole F/g of support, desirablyin the range of from 0.05 to 6.0 millimole F/g of support, and mostdesirably in the range of from 0.1 to 3.0 millimole F/g of support. Thefluorine compound can be dry mixed with the support either before orafter charging to the vessel for dehydration or calcining the support.Accordingly, the fluorine concentration present on the support is in therange of from 0.6 to 3.5 wt % of support.

Another method of treating the support with the fluorine compound is todissolve the fluorine compound in a solvent, such as water, and thencontact the support with the fluorine compound containing solution. Whenwater is used and silica is the support, it is desirable to use aquantity of water which is less than the total pore volume of thesupport.

Dehydration or calcining of the silica is not necessary prior toreaction with the fluorine compound. Desirably, the reaction between thesilica and fluorine compound is carried out at a temperature of from100° C. to 1000° C., and more desirably from 200° C. to 600° C. for twoto eight hours.

The metallocenes, activator and support material may be combined in anynumber of ways. Suitable support techniques are described in U.S. Pat.No. 5,972,823 and 5,643,847, and WO 00/12565.

Regardless of whether the metallocenes and their activator areseparately precontacted or whether the metallocenes and activator arecombined at once, the total volume of reaction solution applied toporous support is less than 4 times the total pore volume of the poroussupport in one embodiment, less than 3 times the total pore volume ofthe porous support in another embodiment, and in the range of from morethan 1 to less than 2.5 times the total pore volume of the poroussupport in yet another embodiment. Procedures for measuring the totalpore volume of porous support are well known in the art. The preferredmethod is described in 1 EXPERIMENTAL METHODS IN CATALYST RESEARCH 67–96(Academic Press 1968).

Methods of supporting ionic catalysts comprising metallocene cations andnoncoordinating anions are described in WO 91/09882, WO 94/03506, WO96/04319 and in co-pending U.S. Ser. No. 09/339,128, filed Jun. 24,1999, now U.S. Pat. No 6,368,999. The methods generally comprise eitherphysical adsorption on traditional polymeric or inorganic supports thathave been largely dehydrated and dehydroxylated, or using neutral anionprecursors that are sufficiently strong Lewis acids to activate retainedhydroxy groups in silica containing inorganic oxide orfluorided-modified supports such that the Lewis acid becomes bound tothe support and a hydrogen of the hydroxy group is available toprotonate the metallocene compounds.

The metallocene supported catalyst system may be used directly inpolymerization or the catalyst system may be prepolymerized usingmethods well known in the art. For details regarding prepolymerization,see U.S. Pat. No. 4,923,833 and 4,921,825, EP 0 279 863 and EP 0 354893.

Polymerization

The metallocene supported catalyst system is useful in coordinationpolymerization of unsaturated monomers conventionally known to bepolymerizable under coordination polymerization conditions. Monomerssuitable for the polymer of the invention include ethylene and C₃ to C₁₂α-olefins. Such conditions also are well known and include solutionpolymerization, slurry polymerization, and low pressure gas phasepolymerization. The metallocene supported catalysts compositions of thepresent invention are thus particularly useful in the known operatingmodes employing fixed-bed, moving-bed, fluid-bed, or slurry processesconducted in single, series or parallel reactors.

The metallocene supported catalyst composition of this invention areparticularly suitable for propylene polymerizations. Any process may beused, but propylene polymerizations are most commonly conducted using aslurry processes in which the polymerization medium can be either aliquid monomer, like propylene, or a hydrocarbon solvent or diluent,advantageously aliphatic paraffin such as propane, isobutane, hexane,heptane, cyclohexane, etc. or an aromatic diluent such as toluene. Thepolymerization temperatures may be those considered low, e.g., less than50° C., desirably 0° C.–30° C., or may be in a higher range, such as upto 150° C., desirably from 50° C. up to 80° C., or at any ranges betweenthe end points indicated. Pressures can vary from 100 to 700 psia(0.69–4.8 MPa). Additional description is given in U.S. Pat. No.5,274,056 and 4,182,810, and WO 94/21962.

Propylene homopolymers may be formed with the metallocene supportedcatalyst composition using conventional polymerization techniques. Themicrostructure of the homopolymer will desirably possess an isotacticpentad fraction as measured by ¹³C NMR of 90% or greater. Copolymerswith ethylene or C₄ to C₁₂ α-olefins may be formed by introduction ofethylene to the propylene slurry or gas phase polymerization of gaseouspropylene and ethylene comonomers. Copolymers with ethylene desirablycontain 0.5 to 10 wt % comonomer in one embodiment, and 1 to 5 wt % byweight of total polymer in another embodiment. Stereoregularhomopolymers and copolymers of α-olefins may be formed with this systemby introduction of the appropriate monomer or monomers to a slurry orbulk propylene process.

Pre-polymerization may also be used for further control of polymerparticle morphology in typical slurry or gas phase reaction processes inaccordance with conventional teachings. For example such can beaccomplished by pre-polymerizing a C₂–C₆ α-olefin for a limited time,for example, ethylene is contacted with the supported metallocenecatalyst composition at a temperature of −15 to 30° C. and ethylenepressure of up to 250 psig (1724 kPa) for 75 min to obtain a polymericcoating on the support of polyethylene of 30,000–150,000 molecularweight. The pre-polymerized catalyst is then available for use in thepolymerization processes referred to above. In a similar manner, theactivated catalyst on a support coated with a previously polymerizedthermoplastic polymer can be utilized in these polymerization processes.

Additionally it is desirable to reduce or eliminate polymerizationpoisons that may be introduced via feedstreams, solvents or diluents, byremoving or neutralizing the poisons. For example, monomer feed streamsor the reaction diluent may be pre-treated, or treated in situ duringthe polymerization reaction, with a suitable scavenging agent. Typicallysuch will be an organometallic compound employed in processes such asthose using the Group 13 organometallic compounds of U.S. Pat. No.5,153,157, WO-A-91/09882 and WO-A-94/03506, noted above, and that ofWO-A-93/14132.

Given that various ionic and/or metallic species are used as catalystsand cocatalysts in the polymerization process, the final polymer mayhave some of these components present. The polymer may be washed (or“deashed”) to remove some or all of these materials. The process ofwashing the polymer is performed after the polymerization process onambient temperature granules or beads of the homopolymer. In oneembodiment, the granules of polymer are washed in a counter current witha solvent such as an alcohol, for example isobutanol(2-methyl-1-propanol), and liquid propylene at a temperature of from 25°C. to 80° C., either in a mixture or alone.

The presence of metals or ionic components in the polymer may bemeasured—before or after washing—by methods known to those skilled inthe art. In one embodiment, the metals can be measured using InductivelyCoupled Plasma Atomic Emission Spectroscopy (ICP-AES) (Jobin-YvonEmission Division of Instrument S.A., Model JY138 Ultrace), whilechloride and silicon ions were determined using X-Ray Fluorescence (XRF)(Philips X-Ray Analytical Co, Model PW1404). The instruments arecalibrated by determining the intensities of a series of knownconcentration standards and fitting those values to a calibration curve.For ICP-AES, the samples to be measured were first ashed, then dissolvedin an appropriate acidic solution, followed by appropriate dilution tofall within the standard calibration curve. For XRF, compression moldedplaques were prepared for chloride (Cl⁻) and Si determination.

Due to the high reactivity of the catalyst system described herein thepolymer and film of the present invention is also characterized inhaving a relatively low level of metal and ionic recoverables both priorto deashing and after deashing relative to prior art methods of makingpolymers and films. The aluminum and chlorine recoverables (combined) ofthe homopolymer of the invention range from less than 25 ppm in oneembodiment, less than 15 ppm in another embodiment, and less than 10 ppmin yet another embodiment. In yet another embodiment, the aluminum andchlorine recoverables ranges from 10 ppm to 25 ppm.

Polymer Films

Films of the metallocene polypropylene polymers of the present inventioncan be formed by conventional processes, preferably by a chill rollcasting process. Referring now to FIG. 1, a simplified schematic diagramof a typical casting apparatus 20 is shown. The polymer is extruded byan extruder 22, melt processed through a slot die 24, and melt drawndown by an air knife 26 and chill roll 28. The resulting polymer film iscollected on a winder 30. The film thickness can be monitored by a gaugemonitor 32, and the film can be edge trimmed by a trimmer 34. One ormore optional treaters 36 and 36′ can be used to surface treat the film,if desired. Such chill roll casting processes and apparatus are wellknown in the art, and are described, for example, in THE WILEYENCYCLOPEDIA OF PACKAGING TECHNOLOGY, (A. L. Brody & K. S. Marsh, Ed.,2^(d) ed., John Wiley & Sons, Inc. 1997).

Preferred films can be formed of the metallocene polypropylenehomopolymers and random copolymers as described above. Typicalcomonomers are selected from ethylene and C₄–C₁₂ α-olefins in oneembodiment, and ethylene and butene in another embodiment. If acomonomer is used, the amount of comonomer is at least 0.5 wt % in oneembodiment, and no more than 10 wt % in another embodiment, and from 1to 5 wt % in another embodiment, the wt % of comonomer-derived unitsbeing relative to the total weight of the polymer.

In addition, polymer blends can be used to form the films of the presentinvention. Such blends can be blends of two or more metallocenepolypropylene polymers as described herein, or a blend of a metallocenepolypropylene polymer and a Ziegler-Natta polypropylene polymer. Polymerblends of metallocene polypropylenes and Ziegler-Natta polypropylenesreadily provide the potential to obtain novel film properties. Thepolymers are miscible, and thus relatively easy to blend. Such blendscan provide enhancements in the clarity, stiffness, tear resistance, andmoisture barrier of the polymer film, while maintaining the good heatsealability of a Ziegler-Natta random copolymer.

Polypropylene cast films of the present invention have severalsignificant advantages over prior art films. For general purpose castfilms, the main processing and product requirements are high output,high line speed and good draw-down, ability to coextrude, efficientquench, ease of surface treatment or embossment, and good filmproperties, such as clarity, moisture barrier, toughness, and goodorganoleptic properties. The narrow MWD of the present metallocenepolypropylene polymers gives resultant films higher cast line speedswithout draw resonance, a lower concentration of low molecular weightextractables/migratory polymer, and a lower concentration of volatiles,and increased thermal processing stability. The narrow compositiondistribution of the present polymers and resultant films enables moreefficient use of comonomer (if desired) in depressing crystallinity(i.e., lower seal initiation temperature), more uniform comonomerincorporation, leading to decreased “sticky” polymer plating-out on filmlines, and a narrower crystal size distribution, resulting in lowerhaze/increased clarity. Finally, a more narrow tacticity distributionresults in low FDA extractables (wider range of packaging opportunities)and potentially stiffer films at the same Tm or SIT (seal initiationtemperature).

In one embodiment, the present invention is directed to polypropylenecompositions suitable for cast film applications as described above, andcast polypropylene films made therefrom. The film resins preferably havea melt flow rate (“MFR”) of from 6–15 dg/min, more preferably of from9–12 dg/min, with a narrow molecular weight distribution, narrowcomposition distribution, and increased film clarity (i.e., decreasedhaze %) compared to prior art Ziegler-Natta polypropylene film resins.In this embodiment, the polypropylene film is cast from an extrudedpolypropylene polymer, the extruded polypropylene polymer being formedby polymerization with a novel fluorided silica supported catalyst asdescribed above. It should be appreciated that these metallocenepolypropylene film resins can be characterized by parameters other thanthe MFR, MWD and CD described above. One skilled in the art will readilyappreciate such parameters, as embodied in the Examples hereinafter,particularly in Examples A–M and the Tables and Figures describedtherein.

In another embodiment, the present invention provides a process forproducing a polypropylene film resin having an MFR of from 6–15 dg/min,preferably of from 9–12 dg/min, with a narrow molecular weightdistribution, narrow composition distribution, and increased filmclarity compared to prior art Ziegler-Natta polypropylene film resins.Further, the xylene extractables (or solubles) level is less than 2 wt %in one embodiment, less than 1.5 wt % in another embodiment, and lessthan 1% in another embodiment, the wt % relative to the total polymer.This is a measure of the level of atactic or amorphous polymer presentin the polymer composition as a whole. The lower the level of xylenesolubles, the more isotactic the polymer.

The process includes the steps of forming a polypropylene polymer bypolymerization of propylene monomers in the presence of a fluoridedsilica supported catalyst, a non-coordinating anion bound to thesupport, and a bis(substituted indenyl) metallocene bound to orassociated with the modified support, and casting the resultantpolypropylene to form a cast polypropylene film having theabove-described properties.

In another embodiment, the present invention provides a polypropylenefilm produced by a process including the steps of forming apolypropylene polymer by polymerization of propylene monomers in thepresence of a fluorided silica supported catalyst, and casting theresultant polypropylene to form a cast polypropylene film.

In another embodiment, the present invention provides articles ofmanufacture formed of or including a cast polypropylene film asdescribed herein.

The advantageous properties described above, as well as others that oneskilled in the art will appreciate from the present disclosure, areillustrated herein in the following examples.

Test Methods

Film Preparation. Cast films were prepared using the followingoperations. Cast monolayer films were fabricated on a Killion cast filmline. This line has three 24:1 L/D extruders (“A” extruder at 2.54 cmdiameter; “B” extruder at 1.91 cm diameter, and “C” extruder at 1.91 cmdiameter), which feed polymer into a feedblock. For monolayer cast filmproduction, polymer was fed only into “A” extruder. The feedblockdiverts molten polymer form the extruder to a 20.32 cm wide Cloeren die.Molten polymer exits the die and is cast on a chill roll (20.3 cmdiameter, 25.4 cm roll face). The cast unit is equipped with adjustablewinding speeds to obtain film of the targeted thickness. Film thicknessdetermined using a profilometer; Haze measured per ASTM D 1003; Glossper ASTM D 2457; WVTR (water vapor transmission rate) per ASTM F 372;Tensile properties and 1% secant modulus by ASTM D 882; Elmendorf tearproperties per ASTM D 1922; Puncture resistance per ASTM D 3420; Totalenergy dart impact resistance per ASTM D 4272.

Molecular Weight and Distribution. Molecular weights and molecularweight distribution (Mw/Mn) was determined using Gel PermeationChromatography.

Melting Temperature. The melting temperature and crystallizationtemperature were determined from peak temperatures from differentialscanning calorimeter (DSC) runs at 10° C./min. heating and coolingrates.

Melt Flow Rate. MFR was determined via the method of ASTM D 1238-95Condition L.

Composition Distribution. The composition distribution analysis ismeasured by a preparative temperature rinsing elution fractionation(TREF) technique in the temperature range of room temperature to 115° C.TREF involves the following steps: dissolving the sample in a goodsolvent, i.e. tetrachlororethylene at 115° C., cooling the dilutesolution slowly to 5° C. at 45 minutes ram time to allow crystallizationon a support, and redissolving and washing the sample from the supportby heating to 115° C. at 30 minutes ram time during elution. Polymerchains are fractionated by difference in their crystallizationtemperature in solution, which is a function of composition. A massdetector provides concentration vs. elution temperature data. Therefore,the separation mechanism is based on differences in the degree ofcrystallinity between copolymer chains. Copolymers with the highestcrystallinity will precipitate out of solution first during the cooling,and will re-dissolove last during heating.

Oscillatory Shear. The viscoelasticity of polymer is determined usingthe Advanced Rheometric Expansion System, ARES, (Rheometric Scientific).Small amplitude oscillatory shear tests were performed utilizing 25 mmparallel plate fixtures at a temperature of 200° C. and over a frequencyrange that was equal to 0.1–100 rad/s.

Recoverable Compliance. This is measured using a Rhemetric StressRheometer. Polymer is melted at 230° C., then stressed at 1×10⁴ dyne/cm²stress for 180 seconds. Then the stress is released to zero to allow thepolymer to recover the deformation. The recoverable compliance is thestrain normalized by the stress recovery.

Xylene Solubles. Xylene solubles were determined by 21 CFR 177.1520(d)(4)(i).

EXAMPLES

The following examples are presented to illustrate the foregoingdiscussion. All parts, proportions and percentages are by weight unlessotherwise indicated. Although the examples may be directed to certainembodiments of the present invention, they are not to be viewed aslimiting the invention in any specific respect. Particular polymerembodiments are labeled either “Sample 1, Sample 2, . . . ” or “S1, S2,. . . ”. Comparative polymer embodiments are labeled either “ComparativeSample 1, Comparative Sample 2 . . . ” or “C1, C2, . . . ”. Embodimentsof using the samples as a film, and testing of their properties, arelabeled either as “Example A, Example B, . . . ”.

Preparation of Fluorided Silica. 48.5 grams of SiO₂ (Grace Davison, asubsidiary of W. R. Grace Co., Conn.) as Sylopol®952 (“952 silica gel”)having a N₂ pore volume 1.63 cc/g and a surface area of 312 m²/g, wasdry mixed with 1.5 grams ammonium hexafluorosilicate (Aldrich ChemicalCompany, Milwaukee Wis.). The ammonium hexafluorosilicate addedcorresponds to 1.05 millimole F per gram silica gel. The mixture wastransferred to a 5 cm ID by 50 cm vycor glass tube having a medium fritplug 3.8 cm from one end. The tube was inserted into a tube furnace andflow of N₂ (220 cc/min) was passed up through the frit to fluidize thesilica bed. The furnace was heated according to the following schedule:

Raise the temperature from 25 to 150° C. over 5 hours

Hold the temperature at 150° C. for 4 hours

Raise the temperature from 150 to 500° C. over 2 hours

Hold the temperature at 500° C. for 4 hours

Heat off and allow to cool under N₂

When cool, the fluorided silica was stored under N₂.

Preparation of Catalyst used for Samples. In a nitrogen purged glovebox, 394.32 grams of fluorided silica was massed and placed in a 3-neck4L reactor equipped with an overhead stirrer. 2L of dry toluene wasadded and the mixture was vigorously stirred. 27.6 ml of N,N-diethylaniline was added via syringe. 86.0 grams of tris(perfluorophenyl)boronwas added as a solid. The mixture was stirred for 1 hour. 5.99 grams ofDimethylsilylbis(2-methyl-4-phenyl indenyl)zirconium dimethyl was addedand the mixture was stirred for 2 hours. The solvent was decanted andthe solid was vacuum dried overnight. Yield: 423 grams. Catalyst loadingwas found to be 0.02 mmol of transition metal per gram of finishedcatalyst.

Sample 1. The finished catalyst composition was oil slurried withDrakeol™ white mineral oil (Witco Chemical) for ease of addition to thereactor. The procedure for polymerizing Sample 1 was as follows. Thepolymerization was conducted in a pilot scale, two reactor, continuous,stirred tank, bulk liquid-phase process. The reactors were equipped withjackets for removing the heat of polymerization. The reactor temperaturewas set at 74° C. in the first reactor and 68° C. in the second reactor.Catalyst was fed at a rate of 1.4 g/hr. TEAL (1 wt % in hexane) was usedas a scavenger at a rate of 4.1 cc/min. The catalyst system preparedabove was fed as a 10% slurry in mineral oil and was flushed into thereactor with propylene. Propylene monomer was fed to the first reactorat a rate of 79 kg/hr and to the second reactor at a rate of 32 kg/hr.Hydrogen was added for molecular weight control at 2400 mppm in thefirst reactor and 3200 mppm in the second reactor. Reactor residencetime was 2.5 hours in the first reactor and 1.9 hours in the secondreactor. Polymer production rates were 29 kg/hr in the first reactor and14 kg/hr in the second reactor. The polymerized granular product wassubsequently washed with liquid propylene fed to the extractor at 45kg/hr flow rate. Polymer was discharged from the reactors as granularproduct having a MFR of 10.0 dg/min. 68% of the final polymer productwas derived from the first stage and 32% of the final polymer productwas derived from the second stage.

Given that catalyst is fed at a rate of from 0.5 to 3 g/hr in anembodiment of the invention, supported fluorided catalyst and fluoridedsupport material will be present in the polypropylene product. In oneembodiment, the support material is present, on a basis of the amount ofsilicon (Si), from 10 to 100 ppm prior to deashing (washing), and from20 to 65 ppm in another embodiment, and from 30 to 55 ppm in yet anotherembodiment.

Sample 2. Sample 2 was prepared in similar fashion as described abovefor Sample 1. The procedure for polymerizing Sample 2 was the same asfor Sample 1 except that propylene monomer was fed to the first reactorat a rate of 79 kg/hr and to the second reactor at a rate of 32 kg/hr,hydrogen was added at 1800 mppm in the first reactor and 2600 mppm inthe second reactor, ethylene monomer was fed to the first reactor at1.77 kg/hr and in the second reactor at 0.73 kg/hr, reactor residencetime was 2.5 hours in the first reactor and 1.9 hours in the secondreactor, and polymer production rates were 16 kg/hr in the first reactorand 14 kg/hr in the second reactor. Polymer was discharged from thereactors as granular product having a MFR of 7 dg/min and containing 2.1wt % of ethylene comonomer. 52% of the final polymer product was derivedfrom the first stage and 48% of the final polymer product was derivedfrom the second stage.

Sample 3. Sample 3 was prepared in similar fashion as described abovefor Sample 1. The procedure for polymerizing Sample 3 was the same asfor Sample 1 except that propylene monomer was fed to the first reactorat a rate of 79 kg/hr and to the second reactor at a rate of 32 kg/hr,hydrogen was added at 1800 mppm in the first reactor and 2600 mppm inthe second reactor, ethylene monomer was fed to the first reactor at2.21 kg/hr and in the second reactor at 0.82 kg/hr, reactor residencetime was 2.5 hours in the first reactor and 1.9 hours in the secondreactor, and polymer production rates were 16 kg/hr in the first reactorand 14 kg/hr in the second reactor. Polymer was discharged from thereactors as granular product having a MFR of 7 dg/min and containing 2.8wt % of ethylene comonomer. 52% of the final polymer product was derivedfrom the first stage and 48% of the final polymer product was derivedfrom the second stage.

Sample 4. Sample 4 was prepared by the physical blend at 1:1 ratio ofmetallocene polypropylene as described in Sample 1 and Ziegler-Nattacopolymer as described in Comparative Sample 2. The polymer blend wasmelt mixed with a 25.4 mm single screw extruder at 227° C. to attain ahomogeneous mix.

Comparative Sample 1. This polypropylene is a commercially availableresin sold by ExxonMobil Chemical Co. (Houston, Tex.), and is catalyzedusing Ziegler-Natta catalyst.

Comparative Sample 2. This polypropylene copolymer is a commerciallyavailable resin sold by ExxonMobil Chemical Co. (Houston, Tex.), and iscatalyzed using Ziegler-Natta catalyst.

Examples A–M

In the following Examples, the metallocene polymers or copolymers arethe polymers or copolymers of the present invention as described in theSamples 1–4 (designated by number) and Comparative Samples (designatedby C#), as described above. The Ziegler-Natta polymers are preparedaccording to conventional methods well-known in the art. In theseexamples, the abbreviation “RCP” is used to indicate a random copolymer,and the abbreviation “Z-N” indicates a Ziegler-Natta polymer.

Example A

This Example illustrates the advantageous feature of the presentmetallocene polypropylene polymers, that the polymers include a very lowconcentration of low molecular weight oligomers, as compared to Z-Npolymers. FIG. 2 shows the molecular weight distribution of ametallocene polypropylene polymer of the present invention having an MFRof 7 dg/min, compared to a Z-N polymer having the same MFR. As theFigure shows, the Mw/Mn of the present polymers is 2.1, significantlyless than the Mw/Mn of 3.7 of the Z-N polymer. The Figure clearly showsa significant low MW “tail” on the Z-N catalyst curve, which is absentfrom the metallocene curve.

Example B

The key structural differences that distinguish the present metallocenepolypropylene polymers from conventional polymers are the narrow MWD,narrow CD, narrow TD (tacticity distribution) and the relative scarcityof chain defects. FIG. 3 shows the composition distribution of aninvention metallocene RCP versus a Z-N RCP. The half width of themetallocene RCP peak is narrower than the Z-N one (4.5 versus 6.8° C.),indicating narrower composition distribution.

Example C

Table 1 shows the properties of typical metallocene homopolymers andrandom copolymers of the present invention, compared to Ziegler-Nattapolymers and copolymers. Metallocene propylene polymer has narrowermolecular weight distribution, lower recoverable compliance, narrowercomposition distribution, and a significantly less xylene extractables.In particular, the recoverable compliance for the polymers of theinvention is from 0.5 to 1.8 (Pa⁻¹×1⁻⁴) in one embodiment, and from 0.6to 1.5 (Pa⁻¹×1⁻⁴) in another embodiment. Further, the MWD (Mw/Mn) isless than 3 in one embodiment, less than 2.8 in another embodiment, andless than 2.5 in yet another embodiment.

Example D

The draw-down potential of polymers was determined by the oscillatoryshear test and can be gauged in a Cole-Cole plot, as shown in FIG. 4, ofloss modulus (viscous strain) versus storage modulus (elastic strain).This representation of the master curve is invariant against the testingtemperature, frequency, and molecular weight. The result of the presentmetallocene polymers having higher viscous strain at a constant elasticstrain illustrates the capability of easier draw-down in the high strainrate process. In contrast, the ultra-high molecular weight components ofZ-N polymers leads to more chain entanglements and therefore lessviscous strain, hindering the rapid draw-down at the high line speed.

Example E

FIG. 5 compares the extrudability of metallocene and Z-N polymers usinga monolayer casting process, using a 89 mm extruder, 107 cm die at 0.635mm die gap, 125 rpm screw speed and 21° C. chill roll. The metallocenepolypropylene offers a comparable extrudability over the Z-Npolypropylene in terms of similar output, extruder load, head pressureand better gauge uniformity across the film width.

Example F

The maintenance of film clarity and gloss during high line speed castfilm processing is a particularly desirable attribute. At higher linespeeds, a deterioration of clarity is often encountered in the priorart, due to the shorter quench time for the melt extrudate and the lessintimate contact of melt curtain on the chill roll. Metallocenepolypropylene polymers offer the advantage of producing clear and glossycast films without compromising line speeds.

A comparison of film properties is shown in Table 2. The narrow MWD andnarrow TD of metallocene polymers results in films having a more uniformdistribution of crystal sizes, which reduces the surface roughness anddiminishes light scattering from the film. As a consequence, the filmclarity and gloss are improved. The films of metallocene polypropylenecombine good stiffness, tensile strength, puncture resistance andmoisture barrier properties of Ziegler-Natta homopolymers with the goodclarity and heat sealability of Ziegler-Natta random copolymers.

Example G

Polymer blends of metallocene polypropylene and Ziegler-Nattapolypropylene readily provide the potential to obtain advantageous filmproperties. The properties of blends of metallocene homopolymers and Z-Nrandom copolymers are shown in Table 3. These properties provideenhancements in clarity, stiffness, tear resistance and moisturebarrier, while maintaining the good heat sealability of Ziegler-Nattarandom copolymers. The total energy dart impact of the blend film is inbetween those of the neat resins.

Example H

This Example illustrates the ability of metallocene polypropylenes toincorporate comonomers uniformly into the polymer backbone. Such abilityopens potential new opportunities to film applications. In the family ofrandom copolymer cast films, the basic requirements include good clarityand sealability. Table 4 shows the film properties of metallocene randomcopolymers and Ziegler-Natta random copolymers. In comparison,metallocene random copolymers have a unique balance of toughness,stiffness, clarity, low extractable content, and good organoleptic andheat sealability.

Example 1

This Example illustrates the ability of metallocene polypropylenes toprovide significantly better extrusion processing stability, with lessvolatiles than the conventional Ziegler-Natta polypropylene. This isdemonstrated by MFR, color and volatiles shifts after multiple extrusionon 25.4 mm single screw extruder at 260° C., as shown respectively inFIGS. 6, 7 and Table 5.

Metallocene polypropylene has less MFR increase after 4-pass extrusions.This is desirable when recycled materials are mixed into the extrusionsystem with the virgin resins. Therefore, the mixed polymer in theextruder is more uniform with metallocene polypropylene thanZiegler-Natta polypropylene.

The high processing stability of metallocene polypropylene is alsoreflected in the lower yellow discoloration of the polymer aftermultiple-pass extrusions, which is also a desirable attribute.

Due to the less low molecular weight oligomers in the metallocenepolypropylene, the volatiles formed after multiple-pass extrusions aresignificantly less with metallocene than Ziegler-Natta polypropylene.This implies less extrusion fuming, die drool and plating out on chillroll of the film processing equipment.

While the present invention has been described and illustrated byreference to particular embodiments, those of ordinary skill in the artwill appreciate that the invention lends itself to many differentvariations not illustrated herein. For these reasons, then, referenceshould be made solely to the appended claims for purposes of determiningthe true scope of the present invention.

All priority documents are herein fully incorporated by reference forall jurisdictions in which such incorporation is permitted. Further, alldocuments cited herein, including testing procedures, are herein fullyincorporated by reference for all jurisdictions in which suchincorporation is permitted.

TABLE 1 Resin properties of propylene Sample and Comparative Samplepolymers. Resin Property S1 S2 S3 C1 C2 MFR (dg/min) 10 7 7 7 7 C₂Comonomer (wt %) 0 2.1 2.8 0 2.8 GPC data Mn (×10³) 78 94 94 64 58 Mw(×10³) 167 203 195 230 212 Mz (×10³) 268 352 309 541 540 Mw/Mn 2.2 2.22.1 3.6 3.7 Mz/Mw 1.6 1.7 1.6 2.4 2.6 DSC data Melting Temp. (° C.) 152135 130 161 146 Heat of Fusion (J/g) 94 89 83 105 76 CrystallizationTemp. (° C.) 115 98 92 112 105 Recoverable Compliance 0.9 1.3 1.3 2.11.8 (Pa⁻¹ × 10⁻⁴) Xylene Solubles (wt %) 0.3 0.6 0.9 3.8 5.1

TABLE 2 Cast film properties - invention Sample and Z-N propylenehomopolymers. Film Property S1 C1 MFR (dg/min) 10 7 C₂ Comonomer (wt %)— — MWD 2.2 3.6 Thickness (μm) 43 41 Haze (%) 2.3 3.9 Gloss @ 45° 85 79Heat Seal Temp. @ 10 N/15 mm (° C.) 140 146 WVTR @ 37.8° C. & 100% RH12.4 13.2 (g/m²/day per 25.4 μm) 1% Sec. Modulus (N/mm²) MD/TD 931/841862/862 Tensile Strength @ YD (N/mm²) MD/TD 21/28 24/25 Elongation @ YD(%) MD/TD 4.8/4.8 4.8/4.8 Tensile Strength @ BK (N/mm²) MD/TD 62/5867/50 Elongation @ BK (%) MD/TD 443/467 411/475 Elmendorf Tear (kN/m)MD/TD 16/21 12/29 Puncture Resistance (kN/m) 929 964 Puncture Energy(kJ/m) 57 52 Total Energy Dart Impact @ 23° C. (J) 0.5 0.3

TABLE 3 Cast film properties - invention Sample and Z-N RCP. FilmProperty S4 C2 MFR (dg/min) 9 7 C₂ Comonomer (wt %) 1.5 2.8 MWD — 3.7Thickness (μm) 46 43 Haze (%) 1.5 1.8 Gloss @ 45° 89 87 Heat Seal Temp.@ 10 N/15 mm (° C.) 136 132 WVTR @ 37.8° C. & 100% RH 14.1 15.8(g/m²/day per 25.4 μm) 1% Sec. Modulus (N/mm²) MD 765 552 TensileStrength @ YD (N/mm²) MD/TD 22/23 18/19 Elongation @ YD (%) MD/TD5.4/5.4 5.3/5.5 Tensile Strength @ BK (N/mm²) MD/TD 57/48 59/45Elongation @ BK (%) MD/TD 681/673 678/669 Elmendorf Tear (kN/m) MD/TD17/21 11/25 Puncture Resistance (kN/m) 876 788 Puncture Energy (kJ/m) 3734 Total Energy Dart Impact @ 23° C. (J) 1.1 2.2

TABLE 4 Cast film properties - invention Samples and Z-N RCPs. FilmProperty S2 S3 C2 MFR (dg/min) 7 7 7 C₂ Comonomer (wt %) 2.1 2.8 2.8 MWD2.2 2.1 3.7 Thickness (μm) 46 46 43 Haze (%) 0.9 0.9 1.8 Gloss @ 45° 9088 87 Heat Seal Temp. @ 10 N/15 mm 128 118 132 (° C.) WVTR @ 37.8° C. &100% RH 14.3 15 15.8 (g/m²/day per 25.4 μm) 1% Sec. Modulus (N/mm²) MD662 600 552 Tensile Strength @ YD (N/mm²) MD/TD 21/20 19/19 18/19Elongation @ YD (%) MD/TD 5.7/5.6 5.6/5.5 5.3/5.5 Tensile Strength @ BK(N/mm²) MD/TD 61/53 60/57 59/45 Elongation @ BK (%) MD/TD 717/728691/717 678/669 Elmendorf Tear (kN/m) MD/TD 17/26 16/26 11/25 PunctureResistance (kN/m) 876 823 788 Puncture Energy (kJ/m) 38 35 34 TotalEnergy Dart Impact @ 2.2 2.4 2.2 23° C. (J)

TABLE 5 Effects of multiple extrusions on volitiles for inventionSamples and ZN propylene homopolymers. S1 S1 C1 C1 Volatiles Virgin 4thPass Virgin 4th Pass C₁–C₅ 0 1  4  4 C₆  0 0  1  1 C₇  0 2 11 13 C₈  0 0 0  0 C₉  0 1  6  6 C₁₀ 0 1  7  7 C₁₁ 0 1  7  7 C₁₂ 11  17  24 31 C₁₃ 00  0  0 C₁₄ 0 1  5  6 C₁₅ 0 1 10 11 C₁₅₊ 1 3 26 26 Total, wppm 13  28 99 112 

1. A process for producing a polypropylene cast film, the processcomprising: (a) forming a polypropylene polymer having an MFR of from 7to 10 dg/min, an M_(w)M_(n) of less than 3, a xylene solubles level ofless than 2 wt %, and a recoverable compliance of from 0.5 to 1.8(Pa⁻¹×10⁻⁴) by polymerization of propylene monomers in the presence of ametallocene supported catalyst system, and (b) casting the resultantpolypropylene to form a cast polypropylene film, wherein the metallocenesupported catalyst system comprises a fluorided support composition anda non-coordinating anion bound to the fluorided support composition. 2.The process of claim 1, wherein the metallocene catalyst is representedby the formula: Cp_(m)MR_(n)X_(q) wherein Cp is a cyclopentadienyl ringwhich may be substituted, or a derivative thereof which maybesubstituted, M is a Group 4, 5, or 6 transition metal, R is ahydrocarbyl group or hydrocarboxy group having from one to 20 carbonatoms, X is a halide, a hydride, an alkyl group, an alkenyl group or anarylalkyl group, m=1–3, n=0–3, q=0–3, and the sum of m+n+q is equal tothe oxidation state of the transition metal.
 3. The process of claim 1,wherein the metallocene is a bis(substituted-indenyl) metallocene. 4.The process of claim 1, wherein the fluorided support composition isselected from fluorided talc, clay, silica, alumina, magnesia, zirconia,iron oxides, boria, calcium oxide, zinc oxide, barium oxide thoria,aluminum phosphate gel, polyvinylchloride or substituted polystyrene,and mixtures thereof.
 5. The process of claim 1, wherein thenon-coordinating anion is selected from fluorinated tris-arylboranecompounds and mixtures thereof.
 6. The process of claim 1, wherein thenon-coordinating anion is selected from tris-perfluorophenyl borane,trisperfluoronaphthyl borane, trisperfluorobiphenyl borane,tris(3,5-di(trifluoromethyl)phenyl)borane,tris(di-t-butylmethylsilyl)perfluorophenylborane, and mixtures thereof.7. The process of claim 1, wherein the polypropylene polymer has axylene solubles level of less than 1.5 wt %.
 8. The process of claim 1,wherein there is from 0.5 to 10 wt % of ethylene or C₄ to C₁₂α-olefin-derived units present in the polymer, by weight of the totalpolymer.
 9. The process of claim 1, wherein the polymer has arecoverable compliance of from 0.6 to 1.5 (Pa⁻¹×10⁻⁴).
 10. The processof claim 1, wherein the polypropylene polymer has an MWD of less than2.5.